1. Field of Invention
This invention is in the field of radiation therapy and more specifically related to use of patient positions to calculate an accumulated dosage.
2. Description of Related Art
To treat cancer, a patient may undergo a radiation treatment known as intensity-modulated radiation therapy (IMRT). During this radiation treatment, a beam of high energy particles and/or x-rays is directed towards a cancerous tumor in the patient in order to kill the tumor. Based on the shape, size, and/or position of the tumor, the beam rotates around the patient and delivers the radiation from different directions according to a dosage delivery model. The dosage delivery model is developed so as to deliver an effective dosage of radiation while minimizing the amount of radiation delivered to healthy locations in the body. The dosage delivery model typically includes a shape of the beam and an amount of radiation to deliver at each beam position.
As is known is the art, a traditional dosage volume histogram (DVH) is oftentimes generated to evaluate the effectiveness of radiation delivered to a patient according to the dosage delivery model. The DVH depicts the amount of radiation received by a specific volume, for example, the heart, lungs, spine, tumor, or the like. To select a dosage delivery model, a doctor can compare DVHs for multiple volumes and/or DVHs based on more than one dosage delivery model.
FIG. 1 depicts an exemplary DVH as is known in the prior art. A curve 110 on the DVH represents the dosage received by a target volume, such as an organ. The curve 110 is interpreted by a doctor as indicating that a dose of at least ten Grays is received by 25% of the total volume of the organ in question. This single data point is typically represented by a histogram 120. Likewise, another data point is represented by a histogram 130. Histogram 130 indicates that a dose of at least 9.5 Grays is received by 50% of the total volume of the organ in question. However, the DVH is based on idealized positioning of the patient and does not account for movement of the patient, thus the relative dosages illustrated by the DVH may have little correspondence to what actually occurs within the patient during radiation treatment.